-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Guy Harris
Sent: August 13, 2007 1:12 PM
To: [email protected]
Subject: Re: [tcpdump-workers] DLT_LAPB value assignment
[EMAIL PROTECTED] wrote:
> There is need to assign DLT_LAPB value for capturing of the X.25 LAPB
> traffic and decoding it in the WireShark Protocol Analyzer.
1Q. So would the packet data in a DLT_LAPB capture start with the
address
field of the LAPB header, followed by the Control field, followed by the
Information field if any?
1A: It's correct LAPB starts with Address, followed by Control, followed
by data if any.
2Q: Or would it also contain an extra flag to
indicate whether the packet is a DTE->DCE or DCE->DTE packet?
2A: LAPB contains direction ( DCE to DTE or vice versa) encoded in the
Address byte. For Layer 3, decoder can decide direction knowing packet(
layer 3) type.
3Q: Would the packets include the CRC at the end?
3A: Currently, in my implementation FCS ( CRC-16) is not included.
4Q: (I'm assuming they would *not* contain the flag octets at the
beginning
and the end, and that all bit-stuffing would have been removed.)
4A: That's correct.
With above set-up WireShark decodes my libpcap captured file, captured
using Sangoma S5142A card.
Best regards,
Mirko Karanovic.
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